Modifying an Existing App to Run on Gigalixir
Whether you have an existing app or you just ran mix phx.new, the goal of this guide is to get your app ready for deployment on Gigalixir.
We assume that you are using Phoenix with Elixir and Gigalixir. If you aren’t, feel free to contact us for help with other frameworks.
However, as long as your app is serving HTTP traffic on $PORT, you should be fine.
Elixir Releases vs Mix
Probably the hardest part of deploying Elixir is choosing which method of deploying you prefer, but don’t worry, it’s easy to change your mind later and switch.
We typically recommend Elixir Releases because it is easy to set up and unlocks the most important features, like Observer.
Here is a comparison table to help you choose.
| Feature | Elixir Releases | Mix |
|---|---|---|
| Remote Observer | YES | |
| Mix Tasks | YES | |
| Built-in to | YES | YES |
| Elixir | ||
| Easy Configuration ¹ | YES | |
| Clustering | YES | YES |
| gigalixir ps:migrate Fast | YES | YES |
| Fast startup ² | YES | |
| Hidden Source Code ³ | YES |
If you choose Elixir releases, see Modifying an App for Gigalixir using Elixir Releases or Phoenix Deploy with Releases.
If you want to use Mix, see Modifying an App for Gigalixir using Mix or Phoenix Deploy with Releases.
¹ We say easy configuration here because some customers get confused about the difference between prod.exs and releases.exs.
² Due to smaller slug sizes and pre-compilation.
³ Mix deploys the source code to the runtime container rather than just the compiled BEAM files
How Do I Switch to Modes?
Mix mode is the default, but we automatically detect automatically detect and switch you to Elixir Releases mode if you have a config/releases.exs file.
To override that behavior, you just need to delete that file.
If you are newer versions of Elixir, you may have a config/runtime.exs file, but not a config/releases.exs.
If you wish to use Elixir Releases, just add an empty config/runtime.exs file to your repoistory.
You can also specify your buildpacks specifically. You can find the default buildpacks for each mode in these docs: